A power electronics inverter normally includes key components such as an insulated gate bipolar transistor (IGBT), a DC Link capacitor, and cold-plate. In the working environment of a vehicle, the maximum ambient operating temperatures are 85° C. (outside of the inverter). The air inside the inverter is considerably warmer, due to waste heat from the operation of electronic components. A challenge with these components is to minimize the internal hot-spot temperature of the capacitor. The useful lifetime of a film-based capacitor's can be approximately doubled by lowering the operating temperature by 10° C. An alternative way to extend the capacitor's useful lifetime is to increase the amount of film, which enlarges the capacitor.
Such a capacitor has a set of electrically conductive bus-bars (typically made of copper) that are mechanically fastened to the terminals of the IGBT. In most known configurations, the bus-bar leads of the capacitor egress one side of the capacitor and their length is kept as short as possible to minimize inductance. See FIG. 1.
There are three primary heat sources that affect the hot-spot temperature of a capacitor, which is typically found deep in the central areas that are furthest from its surface. Heat is generated internally inside the capacitor during its normal operation. The medium surrounding the capacitor (typically hot air) will affect the capacitor's internal temperature. The IGBT in an inverter generates a large amount of waste heat. As a result, most high-power electronic inverters utilize a liquid-cooled cold-plate to conduct the heat from the IGBT out of the inverter. However effective the cooling of the IGBT may be, the internal components will be electrically driven until they are operating at temperatures in the neighborhood of 150° C. The electrical connections between the internal IGBT components and the capacitor must be capable of carrying a large amount of current. Copper is one material that is used to carry the current. Copper also has a high thermal conductivity value and is consequently capable of transferring heat between the IGBT and capacitor. Since the IGBT is hotter than the capacitor, the heat flows into the capacitor, which affects the hot-spot temperature.